Over the recent few years, active study and research have been and continued to be directed to the development of immunosuppressives, which are useful for the study on immunocytes and immune responses and for the treatment of the diseases requiring immunosuppression. For instance, immunosuppressives are utilized in researching almost all of immune responses, including cytokine production, T-cell activation, antibody production, cell death, DNA synthesis, immunocyte differentiation, intracellular signal transduction, etc. The immunosuppressives are also used to treat the diseases attributable to exaggerated immune responses, such as hypersensitive immune response and allergies. In addition, they are needed to suppress excess immune responses upon transplantation of organs, such as the kidney, the liver, the pancreas, marrow, the heart, skin, the lung, etc.
Prevailing immunosuppressives include, for example, cyclosporin A, cyclophosphamide, rapamycin, FK-506, etc. Many immunosuppressives which show similar or different suppressing behaviors are now under research.
The microorganisms belonging to genus Streptomyces or Serratia produce red substances of pyrrolylpyromethene structures, examples of which include prodigiosin, metacycloprodigiocin, prodigiosene, methoxyprodigiosin, and prodigiosin 25-C. They are now known to be of antibacterial and antimalarial activity and, particularly, prodigiosin 25-C shows an immunosuppressing effect.